1. Field of the Invention
The present invention relates to a heat exchanger and a method of manufacturing the heat exchanger. More particularly, the present invention relates to a pin-fin type heat exchanger having an excellent heat transfer efficiency and a method of manufacturing same.
2. Description of the Related Art
It is known to provide a fin around a pipe through which a fluid is passed, to improve a heat transfer efficiency between a fluid passing through the pipe and a fluid passing over the pipe in a heat exchanger. Usually, a plate-like fin is used and is formed on the pipe by winding the plate in a spiral or a ring around the pipe. When the heat exchanger equipped with the plate-like fin is used, a boundary layer of air is generated on a surface of the plate-like fin and this boundary layer remains on the surface of the plate to form a heat insulating barrier and thus it is impossible to obtain a high heat transfer efficiency with this heat exchanger.
To solve this problem, various improvements such as providing a louver or the like, made by providing a hold(s) in the plate-like fin to increase the heat transfer efficiency have been proposed, as disclosed in, for example, Japanese Unexamined Patent Publication (Kokai) No. 56-155391.
A heat exchanger 101 having a plurality of metal pins 104 fixed between two adjacent pipes 103, as shown in FIG. 1(A) and FIG. 1(B), and a heat exchanger 102 provided with a plurality of metal pins 104a and 104b having one end fixed on a pipe 103 and the other end protruded toward an adjacent pipe 103, as shown in FIG. (2), is disclosed in Japanese Unexamined Utility Model Publications 55-145284 and 57-172283. With this method, a heat transfer area of the fins per unit volume of the heat exchanger can be enlarged by increasing the density of the pins on a surface of the pipe through which the fluid passes, and thus the heat exchanging efficiency is increased. Nevertheless, this heat exchanger has a disadvantage in that a pressure loss of a fluid passing around the pipes is increased when the density of the pins is increased. Further, the work necessary to fix the pins on the surfaces of the pipes is cumbersome and requires much time.